High speed developer



United States Patent Ofiice HIGH SPEED DEVELOPER Malon H. Dickerson, Memphis, Tenn., assignor to the United States of America as represented by the Secretary of the Air Force No Drawing. Application June 21, 1957 Serial No. 667,299

1 Claim. (Cl. 96-66) The present invention relates generally to improvements in developing baths for producing photographic images and, as illustrated herein, relates more particularly to high speed developers for high information content negatives.

The production of black-and-white photographic negatives having maximum density and high resolution is particularly important in many fields and especially in aerial photography wherein the detection of relatively minute details is often of great importance. Such photographic negatives are not difficult to produce with soft, slowworking developers which require protracted processing periods to obtain maximum density.

The super-additive effect obtained by combining monomethyl-p-aminophenol sulfate(metol) and hydroquinone in formulae for use as photographic developers has long been known and used. The combination is capable of use in photographic developers of the type called high energy as well as in the softer, slower working developers. However, for adequate development of exposed black-and-White negatives in short immersion periods, the high energy type of developer is not always satisfactory since these developers are usually compounded in baths of extremely high alkali content and high total salts concentration. Development of black-and-white negatives in such baths tends to aggravate the tendency of the silver particles to clump. Such clumping lowers the resolving power of the photographic negative material because it permits movement of the softened emulsion gelation to produce a coarse grained image.

The development of high information content negafives should be carried out in baths which are not excessively alkaline, the maximum permissible alkalinity being approximately pH 10. The formula used must invade the emulsion gelatin as rapidly as possible to obtain full development during very brief periods of immersion in the developer bath. Rapid invasion of the developer is retarded unless the total salts concentration in the developer bath is maintained at a low level.

The present invention contemplates a developing bath wherein the molar ratio of metol to hydroquinone is ap- Patented May 19, 1959 proximately 1:5 and wherein the alkalinity of the bath is maintained at approximately pH 9.8 in the presence of a low concentration of sulfite. The combined effect of the metol and the hydroquinone permits rapid invasion of the gelatin emulsion and provides adequate development of normally exposed aerial film materials in seconds at F. The present formula not only develops maximum density in a normally exposed negative but the resolving power vs. log E curve covers a wide range of exposure at a high level. The high speed of the developing reaction results not only in the production of a photographic negative having adequate maximum density but also produces a negative wherein the grain size compares favorably to that obtained by the use of so-called fine grain developers which requires a development period from 15 to 20 times the development period required by use of the present formula.

The present invention is further illustrated by reference to the following example:

Demineralized Water (90 F.) ml 900 Metol (0.02 mole per liter) g 6.8 Sodium sulfite (anhydrous) g 12.6 Hydroquinone (0.10 mole per 1.) g 11.0 Sodium carbonate (monohydrated) g 49.6 Potassium bromide g 5.9

Demineralized water (90 F.) ml 900 Monomethylparaminophenol sulfate (0.02 mole per liter) g 6.8 Sodium sulfite (anhydrous) g 12.6 Hydroquinone (0.10 mole per 1.) g 11.0 Sodium carbonate (monohydrated) g 49.6 Potassium bromide g 5.9

Demineralized water to make to 1 liter.

References Cited in the file of this patent Photo-Lab-Index, Lester, vol. 1; copy in Div. 60; page 2-14.03 (September 1955), page 3-09 (1951).

Photographic Journal, Section B, vol. 88B, 1948, pages 102-112. Copy in Div. 60 (96/66). 

1. A PHOATOGRAPHIC DEVELOPER COMPRISING: DEMINERALIZED WATER (90*F.) ML 900 MONOMETHYLPARAMINOPHENOL SULFATE (0.02 MOLE PER LITER) G 6.8 SODIUM SULFITE (ANHYDROUS) G 12.6 HYDROWUIONE (0.10MOLE PER 1.) G 11.0 SODIUM CARBONATE (MONOHYDRATED) G 11.0 POTASSIUM BROMIDE G 5.9 DEMINERALIZED WATER TO MAKE TO 1 LITER. 